Correlation of Solid State and Solution Coordination Numbers with Infrared Spectroscopy in Five-, Six-, and Eight-Coordinate Transition Metal Complexes of DOTAM

Sequence-function relationship within water-soluble Peptoid Chelators for Cu2

Chelation of Cu²⁺ by synthetic molecules is an emerging therapeutic approach for treating several illnesses in human body such as Wilson disease, cancer and more. Among synthetic metal chelators, those based on peptoids - N-substituted glycine oligomers - are advantageous due to their structural similarity to peptides, ease of synthesis on solid support and versatile controlled sequences. Tuning peptoid sequences, via systematically changing at least one side chain, can facilitate and control their function. Along these lines, this work aims to explore the role of the non-coordinating side chain within peptoid chelators in order to understand the factors that control the selectivity of these chelators to Cu²⁺ in water medium. To this aim, a set of peptoid trimers having a pyridine group at the acetylated N-terminal, a 2,2'-bipyridine group at the second position and a non-coordinating group at the C-terminus, where the latter is systematically varied between aromatic, aliphatic, chiral or non-chiral, were investigated as selective chelators for Cu²⁺. The effect of the position of the non-coordinating group on the selectivity of the peptoid to Cu²⁺ was also tested. Based on extensive spectroscopic data, we found that the choice of the non-coordinating group along with its position dramatically influences the selectivity of the peptoids to Cu²⁺. We showed that peptoids having bulky chiral groups at the C-terminus enable high selectivity to Cu²⁺. We further demonstrated the ability of one of the selective chelators to remove Cu²⁺ from the natural copper binding protein metallothionein in HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer medium.

Stabilization of two conformers via intra- or inter-molecular hydrogen bonds in a dinuclear vanadium(v) complex with a pendant Schiff base: theoretical insight

A dinuclear vanadium(v) complex, (μ-O)2[V(O)(L)]2, [where HL = 2-methoxy-6-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol] has been synthesized and characterized by spectral and elemental analysis. A single crystal X-ray diffraction study confirms it structure. Two different conformations, stabilized via either intra- or inter-dinuclear hydrogen bonding interactions, co-exist in the solid-state structure. The energies of these intra- or inter-dinuclear hydrogen bonding interactions have been estimated by Density functional theory (DFT) calculations. A 'Non-covalent interaction' (NCI) plot has also been used to characterize these interactions.

Organic amendments affect dissolved organic matter composition and mercury dissolution in pore waters of mercury-polluted paddy soil

Organic amendments (OA) have been applied in many mercury (Hg)-polluted paddy soils to meet increasing food demands with scarce land resources. However, little is known on the effects of different OAs on Hg dissolution and the composition of dissolved organic matter (DOM) in soil pore waters, both of which may be associated with Hg mobility. Consequently, DOM composition and Hg release levels were investigated in soil pore waters after applying food waste compost (FC), fulvic acids (FA) and humic acids (HA) to Hg-polluted paddy soils. FA and HA treatments promoted increased abundances of humic- and fulvic-like substances in pore water DOM while FC amendment increased soluble microbial by-products. FA amendment and high levels of both HA and FC amendments greatly promoted Hg dissolution in pore waters that could be attributed to the complexation of Hg with different DOM components. However, among all DOM components, only UVA fulvic and visible humic-like substances were positively correlated with Hg release levels and total organic carbon. These results indicate that discrepant DOM compositions are induced by different OA. Further, these differences may be associated with differential Hg dissolution in pore waters. Consequently, FA amendment and high level of FC or HA amendments should be limited to reduce potential Hg release into pore waters.

Highly fluorinated metal complexes as dual 19F and PARACEST imaging agents

We reported a set of water-soluble transition metal complexes that can serve as both 19F and PARACEST magnetic resonance imaging agents. The high number of equivalent fluorine atoms and the paramagnetic effect of metals offer these complexes high 19F sensitivity as demonstrated by in vitro19F MRI experiments. The complexes contain carboxamide groups appended onto a cyclen macrocycle, which provide 1H CEST peaks well differentiated from bulk water. The Co(ii) agent displays two CEST peaks that can be utilized for ratiometric pH determination and the concept of combining 19F MR and PARACEST as complementary imaging techniques was demonstrated with the Fe(ii) complex.

Novel primary amide-based cationic metal complexes: green synthesis, crystal structures, Hirshfeld surface analysis and solvent-free cyanosilylation reaction

A new symmetrical and flexible primary amide functionalized ligand, 2,2'-(ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl))diacetamide (2-BPEG), has been synthesized and structurally characterized. Using this multidentate ligand, four novel metal complexes, namely [Cu(2-BPEG)](ClO4)2·0.5H2O (1), [Zn(2-BPEG)](ClO4)2 (2), [Zn(2-BPEG)](ZnCl4)·H2O (3) and [Cd(2-BPEG)(H2O)](ClO4)2·H2O (4), have been synthesized under ambient conditions and characterized by elemental, spectroscopic and thermal analysis, and single and powder X-ray diffraction. Complexes 1-3 are hexacoordinated with an N4O2 donor set (provided by the hexadentate 2-BPEG ligand), while complex 4 is heptacoordinated with an additional coordinated water molecule. In all cases, the 2-BPEG ligand acts as a hexadentate ligand. A change in the starting metal salt has resulted in the formation of 2 and 3 with different tetrahedral anions, ClO4- and ZnCl4-, respectively. This has provided an opportunity to showcase anion-directed supramolecular networks for these compounds. Compounds 1, 2 and 4 with perchlorate anions show similar and comparable intermolecular interactions in their 3D networks. On the other hand, the supramolecular self-assembly of 3 is dominated by a variety of intermolecular interactions such as C-HCl, N-HCl, O-HCl and C-HO due to the presence of a tetrachlorozincate(ii) ion. Moreover, the role of weak intermolecular interactions in the crystal packing has been analysed and quantified using Hirshfeld surface analysis. Furthermore, compound 4 exhibiting an open Lewis acid site has been found to be a very efficient and recyclable heterogeneous catalyst for the solvent-free cyanosilylation of various aldehydes with trimethylsilyl cyanide (TMSCN) producing the corresponding trimethylsilyl ether in high yields.